Post-transcriptional modification of RNA plays an important role in controlling expression of genes and impacts on developmental processes. This control may occur at various levels or stages, such as, for example, mRNA transport out of the nucleus, splicing, polyadenylation, RNA degradation, among others. The regulation is achieved by RNA-binding proteins which may act directly on the RNA or indirectly through association with other proteins. RNA-binding proteins are characterised by the presence of an RNA-binding domain. Most of the heterogeneous nuclear ribonucleoproteins (hnRNP) have an RNA-binding domain known as “RNA recognition motif” (RRM-domain). Another widespread RNA-binding domain is known as the K homology motif (KH-domain), and is found in proteins involved in transcription, mRNA stability, translational silencing and mRNA localisation. For a discussion of various RNA-binding domains, see Burd and Dreyfuss (Science 265, 615-621, 1994).
RNA-binding domains may be present in combination with other domains, such as zinc fingers, ring finger domains, RS domains or NTF-like domains like the “nuclear transport factor 2” (NTF2) domain. Proteins with an NTF2 domain are known to play a role in trafficking of macromolecules, ions and small molecules between the cytoplasm and nucleus.
Hisashi et al. (JP 2005-185101) disclose over 28000 rice cDNAs of which about 75% was annotated through homology with Arabidopsis thaliana sequences. It was postulated that these sequence could be useful to create plants with different characteristics compared to their wild-type equivalents. WO 2004/035798 discloses genes that are upregulated or downregulated in transgenic plants overexpressing E2Fa/DPa and the use of such sequences to alter plant characteristics. Both patent applications disclose a GSBP-like protein, however none of them teaches how to increase seed yield of a plant by preferentially expressing a GSBP-like protein in the root.